Interrogation of the Plasma-Catalyst Interface via In Situ/Operando Transmission Infrared Spectroscopy

Abstract

Plasma-surface coupling has emerged as a promising approach to perform chemical transformations under mild conditions that are otherwise difficult or impossible thermally. However, a few examples of inexpensive and accessible in situ/operando techniques exist for observing plasma-solid interactions, which has prevented a thorough understanding of underlying surface mechanisms. Here, we provide a simple and adaptable design for a dielectric barrier discharge (DBD) plasma cell capable of interfacing with Fourier transform infrared spectroscopy (FTIR), optical emission spectroscopy (OES), and mass spectrometry (MS) to simultaneously characterize the surface, the plasma phase, and the gas phase, respectively. The system was demonstrated using two example applications: (1) plasma oxidation of primary amine functionalized SBA-15 and (2) catalytic low temperature nitrogen oxidation. The results from application (1) provided direct evidence of a 1% O2/He plasma interacting with the aminosilica surface by selective oxidation of the amino groups to nitro groups without altering the alkyl tether. Application (2) was used to detect the evolution of NOX species bound to both platinum and silica surfaces under plasma stimulation. Together, the experimental results showcase the breadth of possible applications for this device and confirm its potential as an essential tool for conducting research on plasma-surface coupling.

The Removal of CH4 and NOx from Marine LNG Engine Exhaust by NTP Combined with Catalyst: A Review

“…In 2017, Du et al [33] measured the temperature distribution in the IPC reactor during the CH 4 /CO 2 reforming process based on the OES of CO(B 1 Σ + →A 1 Π). In 2022, Clarke et al [34] designed an IPC reactor capable of connecting with Fourier transform infrared spectroscopy (FTIR), OES, and mass spectra (MS), while characterizing the catalyst surface, plasma, and gas phase, as shown in Figure 4. Using this system, the evolution of NO x species bound to Pt/SiO 2 surfaces under plasma action was detected.…”

In Situ Ambient Pressure Photoelectron Spectroscopy Study of the Plasma–Surface Interaction on Metal Foils

“…Investigations into this plasma–surface interface are therefore greatly sought to deepen our understanding of the surface chemistry occurring in a plasma environment. Although in situ techniques such as Raman spectroscopy , and IR spectroscopy have been applied, one powerful chemical analysis technique for surface characterization currently not implemented in situ is X-ray photoelectron spectroscopy (XPS), as it is traditionally operated in a high vacuum. As such, previous investigations on the plasma–surface interface perform ex situ measurements by exposing the sample to the plasma environment before returning to vacuum conditions for XPS measurements. − While these ex situ XPS measurements provide vital information regarding the post-plasma surface chemistry, it cannot fully describe the intermediate chemical reactions or temporary chemical states that occur during the plasma environment.…”

Self-Organization and Nitrogen Incorporation in Diamond-Like Carbon Microstructures Synthesized by Nonthermal Plasma

“…The development of carbon-neutral technologies for point-source conversion of gaseous alkanes (e.g., biogas and shale gas) to energy-dense products and green hydrogen has received considerable attention in recent years. − Nonthermal plasma stimulation has emerged as a promising solution owing to its ease of coupling with renewable sources of electrical energy combined with its unique ability to reform natural gas at ambient conditions through inelastic collisions with high-energy electrons . In a typical setup, an annular dielectric barrier discharge (DBD) plasma is combined with an appropriate catalyst in either a one- or two-stage process, resulting in enhancements to both the overall activity and product selectivity. − However, plasma-driven C–H and C–C bond scission in light alkanes leads to the uncontrolled formation of coke, which negatively affects the performance of both the catalyst and the plasma and presents a major barrier to commercial implementation. , Thus, achieving an advanced understanding of carbon deposition in plasma reactors and developing strategies to mitigate this issue are critical steps toward the realization of an industrial plasma-catalytic process for light alkane valorization.…”